7 things you never knew people could be allergic to - and the insane ways they cope

We're all familiar with allergies - in the US, approximately 30% of adults and 40% of children suffer from them, and they are unfortunately getting worse for many.

These reactions are triggered by immune system responses to substances that are generally considered harmless. Symptoms range from itchy eyes and runny noses to skin hives to life-threatening, throat-closing anaphylaxis.

Most people are aware of common allergens like pollen, peanuts, dogs, and cats. But allergy and immunology specialists sometimes encounter more mysterious allergies.

Here are some of the strangest and rarest allergies doctors encounter - and how patients with these conditions try to cope.